A conventional catheter-type electrode member, to be used as part of a cardiac pacemaker, includes an insulated conductor whose dielectric sheath terminates in a flat platform-shaped pad, the conductor having a straight tip projecting from that pad for insertin into the heart muscle which for this purpose must be perforated beforehand. To maintain this projecting tip within the perforation in the heart muscle, it is necessary to suture the platform to the heart muscle after insertion in order to prevent any dislodgment of the tip by the movement of the heart muscle.
With a view to more firmly anchoring the conductor tip to the heart muscle, it has been proposed to give it the shape of a helix. This has the drawback that its insertion in the heart muscle requires the preliminary drilling of a rather large hole therein. It is furthermore extremely difficult to predetermine the correct length of the conductor tip to be inserted, in order to keep it from penetrating the ventricular chamber. Moreover, the conductor has a tendency to break at the point where the helix enters the heart. Finally, the surgeon has to prepare at the start of the operation a rather substantial access opening in the thorax enabling the helix to be threaded into the muscle by rotating it about its axis. For proper penetration that axis must be substantially perpendicular to a plane tangent to the heart-muscle surface at the point of insertion, this condition greatly complicating the task of the operator.